The present invention relates to compaction equipment for commercial and industrial trash compaction to facilitate refuse disposal and to waste paper baler equipment utilized in paper recycling, both of which are important and widely used tools in the field of waste management. It is very desirable that this equipment be both efficient and reliable. As with all powerful mechanical equipment, safety hazards should be eliminated to the maximum extent possible, recognizing that there is a tendency for human operators to be less careful than they should be.
Although the invention with which this application is concerned is useful in both waste paper balers and in trash compactors, this background discussion will primarily concern itself with trash compactors, since they are possibly the more widely used and common form of equipment. The detailed description below will also fully describe balers incorporating the invention. The commercial or industrial trash compactor which will be referred to herein simply as "trash compactor" is found in many situations where there are large volumes of waste to be disposed of in landfills or other waste disposal facilities. Thus, trash compactors are found in shopping centers, industrial complexes, associated with large discount stores or department stores, and in some residential complexes.
The use of trash compactors has obvious advantages over the common dumpster, the capacity of which is limited to the amount of uncompacted waste which the dumpster's volume will accommodate. When a trash compactor is utilized for waste management, a trash compaction apparatus is provided with which is associated a container. As the trash is introduced, it is compressed by the compactor, typically reducing its volume by from three to ten times. This greatly reduces the frequency with which the trash container must be hauled to a landfill or other place of disposal, thereby greatly reducing the cost of disposal.
Typically, when the container is full or partially full, it is loaded on a specially configured truck which may also deliver an empty container to be placed on the trash compactor. The contents of the trash container are transported to a landfill or other suitable disposal site. A further advantage may be accrued by the compaction of the trash in terms of the efficiency with which it may be disposed of by the landfill operation, incineration operation, or the like.
It is known to provide means of varying degrees of complexity to determine when the trash container associated with the compactor is full or nearly full. One common method of determining when the trash compactor is full involves a measurement of the resistive force encountered by the ram which, of course, rises to a high level when the trash in the container has been compacted to nearly the maximum extent possible. Various means have been employed for making a direct or indirect determination of the resistive force encountered by the ram; these include the use of a conventional strain gauge, measurement of the hydraulic fluid pressure, and measurement of the motor current drawn by the pump motor for the compaction equipment hydraulic system.
Although operational control of compaction apparatus in years past was usually implemented by simple switches and relays, there has been a tendency in recent years to employ computer microprocessors and somewhat sophisticated computer programs and algorithms stored in computer memory in or associated with the microprocessor. In computer systems complex algorithms are often employed wherein there were multiple resistive force measurements or wherein the rate of change of the resistive force or the derivative of the signal representing resistive force is employed to endeavor to improve on the measurement of fullness provided by the compactor.
U.S. Pat. No. 4,953,109 to Burgis, U.S. Pat. No. 5,016,197 to Neumann, et al. and U.S. Pat. No. 5,558,013 to Blackstone, Jr. are examples of trash compaction systems utilizing rather complex computer programs to implement the desired control system, including fullness determination, in compaction apparatus. These may be compared with U.S. Pat. No. 3,802,335 to Longo and U.S Pat. No. 4,643,087 to Fenner et al. which do not employ computer microprocessors but execute simple logic with electrical relays.
Trash compactors are typically exposed to harsh environments including wide ranges of outdoor temperatures and potential exposure to power surges. In addition, it is very important that the compaction equipment operate reliably and operate in a safe manner and not be subject to malfunction because of failure or error conditions in its electrical controls. For that reason, there are many users and others who consider that a relatively simple relay based control system has advantages with regard to reliability, durability and safety over available microprocessor controlled compaction systems.